Not Applicable.
This invention relates in general to hub assemblies, and more particularly to a hub assemblies with surfaces that rotate with essentially no runout and a process for producing the same.
Most passenger automobiles and light trucks of current manufacture come equipped with disk brakes, at least at the front wheels of such vehicles. Disk brakes weigh less than drum brakes, which they have to a large measure replaced, are less expensive to manufacture, are easier to service, and provide more effective braking. But disk brakes will produce annoying pulsations, known as xe2x80x9cbrake judderxe2x80x9d, if improperly manufactured or maintained.
The typical disk brake for a vehicle has a disk which rotates with a road wheel of the vehicle and a caliper which clamps down on the disk when the brakes of the vehicle are applied. Indeed, the caliper has pads which bear against machined surfaces on two sides of the disk, with the friction between the pads and the machined surfaces providing the braking. The machined surfaces must be perfectly flat, and must rotate without runout (wobble), lest brake judder will develop when the brakes are applied.
Various arrangements exist for mounting the road wheelsxe2x80x94and the brake disks as wellxe2x80x94on the suspension systems of the vehicles. In one the road wheel and brake disk for that wheel are bolted to a hub having a spindle which rotates in an antifriction bearing which in turn is fitted to a housing. The housing is attached to a steering knuckle or other component if the vehicle""s suspension system. The disk, being a separate and relatively simple component is easily machined to close tolerances along its critical surfaces. But that surface of the hub against which the brake disk is installed does not lend itself to the same precision. To be sure, it is machined, but the machining occurs before assembly, so the bearing on which the hub rotates and the surface on which it is mounted can all contribute to runout in the surface against which the brake disk is installed. This runout transfers to the brake disk itself.
The present invention resides in a process for providing the rotating hub of a hub assembly with a mounting surface that is essentially free of runout, so that a brake disk installed against that surface will not acquire runout from the hub assembly. The hub has a spindle which rotates on a bearing in a housing, both of which also form part of the hub assembly. At one end of the spindle the hub has a flange provided with a face which is presented away from the housing. That face is machined while the housing is held fast and the hub is rotated on the bearing, and as a consequence the face, which is the mounting surface, rotates with essentially no runout. The invention also resides in a process for assembling a hub assembly and also in the hub assembly itself.